Automatic feed mechanism for machine tools, especially grinding machines



Sept. 20, 1955 HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed 0012. 31., 1952 9 Sheets-Sheet l INVENTOR ERIC GEORG HJARPE BY HIS ATTORNEYS Sept. 20, 1955 HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed 001). 51, 1952 9 Sheets-Sheet 2 i] WI INVENTOR ERIC GEORG HJARPE Sept. 20, 1955 E. G. HJARPE 2,713,100

AUTOMATIC FEED MECHANISM FOR MACHINE LLY GRINDING MACHINES TOOLS, ESPECIA 9 Sheets-Sheet 3 Filed Oct. 31, 1952 INVENTOR ERIC GEORG HJZKRPE BY HIS ATTORNEYS WW p 1955 E. G. HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed Oct. 31, 1952 9 Sheets-Sheet 4 INVENTOR ERIC GEORG HJARPE BY HIS ATTORNEYS Sept. 20, 1955 E. G. HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed Oct. 51, 1952 9 Sheets-Sheet 96 m W124 9'7 I 125 INVEN'IOR ERIC GEORG HJARPE BY HIS ATTORNEYS Sept. 20, 1955 E. G. HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed Oct. 51, 1952 9 Sheets-Sheet e INVEN'TQR ERIC GEORG HJARPE BY HIS ATTORNEYS S pt. 1955 E. G. HJARPE 2,718,100

AUTOMATIC FEED MECHANISM FOR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES Filed Oct. 31, 1952 9 Sheets-Sheet 7 w i g INVENTQR ERIC GEORG HJARPE BY HIS ATTORNEYS p 1955 E. G. HJARPE fil fififi AUTO TIC FEE EC NISM FOR MACHINE TOO ESPECI Y INDING MACHINES Filed Oct. 31, 1952 9 Sheets-Sheet 8 Fig. 12.

INVENTOR ERIC GEORG HJARPE BY H IS ATTORNEYS W hzmzm/ Sept. 20, 1955 E. G. HJARP 2,718,100

AUTOMATIC FEED MECHANIS OR MACHINE TOOLS, ESPECIALLY GRINDING MACHINES 7 Filed Oct. 51, 1952 9 Sheets-Sheet 9 INVENT'OR ERIC GEORG HJARPE BY HIS ATTORNEYS United States Patent 1 2,718,100 AUTOMATIC FEED MECHANISM FOR MACHINE TGOLS, ESPECTALLY GRENDING MACHINES Eric Georg Hiiirpe, Goteborg, Sweden, assignor, by rnesue assignments, to SKF Industries, Inc., Philadelphia, Pa., a corporation of Deiaware Application October 31, 1952, Serial No. 318,122 Claims priority, application Sweden November 3, 1951 Claims. (Cl. 51-165) In grinding work pieces in the form of bodies of revolution it is necessary, in order to permit the insertion of a new work piece, that the grinding-wheel carriage be retracted from the working position sufliciently to permit the work piece to be introduced into the chuck and caused to rotate without coming into contact with the grinding wheel until the automatic feed has been connected. A certain margin of safety must always be provided for because of variations in the diameter and excentricity of the work piece.

In machines of the usual type the work piece is first inserted in the chuck after which the operator feeds the grinding-wheel carriage forwards by hand to a position in which the grinding-wheel is immediately adjacent to the work piece. Only when this has been done is the automatic feed started.

In completely automatic machines, however, this comparatively quick manual feeding cannot be utilized. Instead the automatic feed must also function when the grinding-wheel is not actually engaged with the work. Since the automatic feed, as a rule, is less than 1 mm./min., it is apparent that there will be a considerable loss of time, since no material is being removed during the period in which the grinding-wheel is being fed toward the work piece.

The present invention relates to a device which automatically governs the feed of the wheel carriage so that it is much faster as long as the grinding-wheel has not come into contact with the work, but assumes a preadjusted normal rate at the moment the grinding-wheel contacts with the work piece.

The invention is illustrated on the accompanying drawings in which Fig. 1 shows mainly in diagrammatic form the devices for chucking the work piece. Figures 2, 3 and 4 show cam devices for governing the valves of the hydraulic mechanism. Fig. 5 is a partial section through the grinding-wheel spindle and its motor and Fig. 5a a cross section through the coupling between the motor axle and the grinding-wheel spindle. Fig. 5b is a cross section through a portion of the motor shield 28. Fig. 6 shows diagrammatically the pump and governing valves for the feed piston of the grinding-wheel carriage. Figs. 7 and 8 show in different positions hydraulic pistons for the mechanism for introducing and ejecting the work piece. Figures 914 show various positions of the valves r' of the hydraulic system.

Parts of the mechanism which do not directly concern the invention are only indicated. For instance the ejector mechanism and the mechanism for inserting work pieces are indicated only by the driving mechanism with a rack and pinion.

In Fig. l, the work piece 1 is held between the spindle 3 of the work carriage and a center point 4. The work spindle 3 is driven by a motor 5. A gaging finger 6 is urged by a spring 7 in a clockwise direction about its axle 8, but is prevented from carrying out this movement by the work piece 1, as long as the work piece has a diameter greater than that for which the mechanism is adjusted. As long as the gaging finger 6 is prevented from swinging by the work piece 1, a circuit in which a pair of electromagnets 9 and 23 (Figures 2 and 3) are connected is broken, but when the finger can pass the work piece 1, the

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circuit is closed by a pin 10, as shown in Fig. l. The grinding-wheel 11 is fixed to a spindle 12 (Fig. 5) which is carried in bearings on a carriage 14 movable on the frame 13. The carriage 14 is provided with a cylinder 15, in which is a piston 16 connected to the frame 13 by means of a bar 17. A motor 18 mounted under the carriage 14 is provided with a shaft 19, which is coupled to the grinding-wheel spindle 12 through a torsion bar 20 and also through a coupling member 21 on the motor shaft 19 and another coupling member 22 on the grinding wheel spindle 12.

Between the teeth of the two coupling members 21 and 22, there is a certain amount of play, A, which remains unaltered, as long as the torsion bar 20 alone can transmit the torque required to drive the grinding-wheel 11. If the torque thus required is so great that the torsion bar 20 is twisted a certain angle, the coupling members 21 and 22 will turn relative each other, whereby the play will partially or completely disappear and a corresponding play arise in the opposite direction. A bar 24 is located within the motor axle 19 and is at its upper end carried by three rollers 25 in such a manner, that it rotates at the same speed as the motor axle 19, but can be axially displaced a short distance relative the latter.

The lower end of the bar 24 is mounted in a ball bearing 26, the outer race ring of which is fitted in a housing 27 connected to a metal diaphragm 29 connected to the motor shield 28. When the coupling members 21 and 22 turn relative each other, pins 30 connected to the coupling member 22 actuate the rollers 31, so that the bar 24 is pressed downwards whereby the housing 27 presses against an electric switch 32 (micro-switch) causing the latter to close a circuit shown in Fig. 6 in which is connected an electro-magnet 72.

A number of piston valves 38, 39, 46, 41, 42 and 4-3 (see Fig. 9) are each manoeuvreable by means of cams, mounted on a common cam shaft 37 (Figures 24) driven by a motor 133 through worm wheel gearing 94 and 95 and a one revolution coupling 48 and 49, having a pawl 48, which is disconnected from the ratchet 49, as soon as an arm 45 comes into contact with either of a pair of pins 46 and 50 on an arm 44. All the valves 38-43 are actuated by the cams in the manner, as shown in Fig. 2, except that valves 38, 39 (Fig. 9) are provided with pawls 33 actuated by the electro-magnet 23 (Fig. 2).

The movement of the grinding-wheel carriage 14 (Fig. 5) takes place under the influence of hydraulic pressure in the following manner. Pressure fluid is admitted to the valve 38 (Fig. 9) through a channel 51 and flows through a chamber 52 and a channel 53 to a cylinder chamber 54 (Fig. 5 Further pressure fluid flows through a channel 55 (Fig. 6) past a needle valve 56 to an annular channel 57 and channels 58 into the chamber 60 of a valve 59 and further through channels 61 to an annular channel 62 and from there through channels 63 and 64 to the valve chamber 65 (Fig. 9) through a channel 66 to a cylinder chamber 67 (Fig. 5). A small separately driven piston pump 68 (Fig. 6) is provided in which the capacity can be varied by adjusting the length of the stroke by means of a screw 69. The fluid delivered by this pump flows past ball valves 70 into a channel 71, where it joins fluid, which as described above, flows through the channel 64 to the cylinder chamber 67 (Fig. 5).

Since the effective piston area in the cylinder chamber 67 is about twice as great as the piston area in the cylinder chamber 54, the grinding wheel carriage 14 will be moved to the right at a speed determined by the amount of fluid, which can pass the needle valve 56 (Fig. 6), plus the amount of fluid delivered by the piston pump 68. During the time which the electromagnet 72 is active, it keeps the valve 59 in raised position, as shown in the drawing. During this interval, the pressure fluid cannot sure in this chamber is determined by the spring 74 of the Fig. 10), which is so adjusted that the valve pecific pressure, which is halt as great as om the channel 55 to the channel 63 and thus the )f the grinding-wheel carriage 14 depends only on ball valve 73 pacity of the pump 68. This speed is that which 73 opens for a s has been called the normal feed. When the valves the pressure on the pressure fluid, which has been introare in the position shown in Fig. 10, the grindingduced into the cylinder chamber 54- (Fig. 5) through the carriage 14 will not be fe inlet 51 (Fig. There is thus equilibrium between 74 of the ball valve 73 is so adjusted that the spethe pressures acting on the piston surfaces in both the cylinder chambers 54 and 67. The grinding wheel carluid pressure in a ciannel 75 and thus in a cylinder riage 14 is now stationary. The electro-magnet 9 (Fig. 3)

ber 67 (Fig. 5) is only half as great as 1n the inlet iels, which are in communication with the cylinder 10 which became activated upon the turning of the finger 6 e the cylinder (Fig. 1) brings the lever 44 into such a position that .ber 54. The pressures acting upon L in both the cylinder chambers 54 and 67 keep the pin 46 loosens the arm which is then turned antilosed in chamclockwise by the spring 47 other in equilibrium, even if air is enc will engage the ratchet wheel 49 and the cam shaft 37 is 'hich the valve 39 is shown in ig. turned anticlockwise by the worm gear 94 and 95. This e turning movement is interrupted when the arm 45 engages the other stop 50 of the lever 44, the cams of the cam shaft 37 having during this rotation acted upon valve iston 79 against an ad 38-43, so that the relative positions of the valves is now able stop 86. The quantity of fluid required for this 30 that shown in Fig. l

the cylinder cham- Through the altered position of the valve 42, the cylin- 67 (Fig. 5) under the influence of the pressure in the der chambers 96 and 97 of the ejector and work piece inder chamber 54 and the grinding-wheel 11 has thus inserting mechanisms (Fig. 7) have been put in corn en moved from the work piece 1 a corresponding dismunication with the outlet through channels 98, 99 and 25 100, the valve chamber Till and a channel 107. (Fig. 10). The valve 43 (Fig. 9) governs the flow of air pressure Since the cylinder chambers 103 and 104 are always under a cylinder chamber 81 (Fig. l) in pressure through channels 105 and 106, the pistons 107 hich exerts the pressure on a member 83 which 15 necand 108 in these chambers will be pressed in toward the ;sary to enable the center poin smaller pistons 169 and 119, as shown in Fig. 8. A pair iece 9 in correct position against a holder on the work 30 of gear wheels 111 and 112 are pindle wise and clockwise respectively, whereby the ejector and hich the cylinder chamber 81 is in communication workpiece-inserting-mechanisms (not shown) are moved 7 atmosphere t n 2 and the mandrel 83 to the immediate vicinity of the working spindle. In this he pisto S U nd the Work position, the grinding wheel 11 (Fig. 1) contacts the work I W 'nstt e latter. The length Wfi/flfl/W/jamv/l /i M Mm ninth chm c1 l i l l .7 l ill/11ml) I H W M l j illi/militia limit through a channel 130, the valve chamber 131 and a channel 132 and the spring 84 presses the piston 82 and the mandrel 83 upwards and the point 4 releases the work piece 1.

During the continued rotation of the cam shaft 37 cams have acted upon the valve 41, so that the relative positions of the valves is now that shown in Fig. 12. Pressure fluid now flows through a channel 122, the valve chamber 119, channels 118 and 117 to a cylinder chamber 116 (Fig. 8) and moves the pistons 110 and 108 to the right, as far as the piston 110 can move. The driving wheel 112 of the ejector mechanism has thereby been rtated counterclockwise through a certain angle, which thus removes the ejector mechanism together with the work piece. Immediately thereafter during the rotation of the shaft 37, cams act upon valves 40 and 43 so that the relative positions of the valves is according to Fig. 13.

A cylinder chamber 123 (Fig. 8) is now in communication with the outlet through channels 124, 125 and 126, a valve chamber 127 and channels 128 and 129. The pressure in cylinder chamber 103 is sufficient to move the pistons 107, 108 to the right, whereby the driving wheel 111 of the work inserting mechanism is turned counterclockwise and the work inserting mechanism (not shown) transports a new work piece to a position opposite the centre point 4 (Fig. 1). An air pressure inlet 133 in a valve 43 has been put into communication with the cylinder chamber 81 through a valve chamber 131 and a channel 130. The piston 82 is thus moved downwards together with the mandrel 83, whereby the centre point 4 engages the centre hole of the work piece and presses the work piece 1 against the supporting plate 134 of the work spindle 3. Upon continued rotation of the cam shaft 37 other cams have acted upon valves 40, 39 and 38, whereby the positions of the valves is now that shown in Fig. 1

In their new positions the valves 38 and 39 are again held by the pawls 33 (Fig. 2) and are thus retained in their positions by the latter even after their cams have lost contact with the rollers 36 of the levers 35. At the same time, as the valves 38 and 39 are displaced, the switch 115 (Fig. 4) which is also manoeuvred by a cam on the cam shaft 37 starts the electromotor 5 (Fig. 1), so that the work spindle 3 and the work piece 1 Will rotate. In the new positions of the valves 38 and 39 (Fig. 14), pressure fluid again reaches the cylinder chamber 67 (Fig. 5) through the inlet channel 55 (Fig. 6), the needle valve 56, the annular channel 57, channels 58, 61, 62, 63, 64 and 93, the valve chamber 65 and a channel 66. The fluid pressed out into the channel 71 by the pump 68 also flows through the same channels.

Pressure fluid reaches the cylinder chamber 54 through channels 51 and 92, valve chamber 52 and channel 53. Because of the greater piston area in the cylinder chamber 67, the grinding wheel carriage 14 is moved toward the right, in other words, the grindingwheel 11 approaches the work piece 1 at a speed determined by the rate of flow past the needle valve 56 and the capacity of the pump 68.

As soon as the grinding-wheel 11 comes into contact with the work piece 1, a resistance is set up at the periphery of the grinding wheel, which tends to diminish the speed of the grinding-wheel. Hereby the torsion bar (Fig. 5) is twisted and a relative movement takes place between the coupling member 21 of the motor shaft and the coupling member 22 of the grinding-wheel spindle, whereby the pins 30 in the coupling member 22 of the grinding-wheel spindle press the rollers 31 downwards, taking with them the bar 24 in the manner previously described. The switch 32 is thus caused to close a circuit activating the electro-magnet 72 (Fig. 6) and the latter then lifts the valve 59 to its upper position, shown in the figure. The pressure fluid which passes the needle valve 56 is thus prevented from passing the valve 59 and only pressure fluid from the pump 68 now reaches the cylinder chamber 67.

Upon continued rotation of the cam shaft 37, the valve 42 is shifted so that the valves now again assume the position shown in Fig. 9.

Pressure fluid now flows to the cylinder chambers 96, 97 and moves the pistons 107, 108 to their outer positions, as shown in Fig. 7. In other words, the gear wheel 112 has been turned clockwise, whereby the ejector releases the work piece removed from the work spindle 3 and the gear wheel 111 has been turned clockwise. The work introducing mechanism has picked up a new work piece. The cam shaft now stops in this position because the arm 45 (Figures 2 and 3) engages the stop pin 46. The mechanism has now returned once more to the position assumed at the beginning of the cycle described above which will be repeated continuously. The valve 51 (Fig. 6) can move downwards only slowly because the fluid in a chamber 136 can only pass a ball valve 137 at a certain adjustable speed, but can pass quickly in the opposite direction.

Since the valves 3843 are not directly acted upon by the cams of the cam shaft 37, but only through the levers 35, the valves 3843 can be manually adjusted independently of the positions of their respective cams. The various movable members of the machine can thus be caused to carry out their movement manually and independently of each other.

I claim:

1. In a machine tool, a rotary tool, work supporting means, mechanism for feeding the tool towards the work, a drive motor for the tool, a torsion bar connected at one end to the motor and at the other end to the tool, said bar being dimensioned so that it is capable of rotating the tool when the latter is not in working contact with the work but not capable of rotating the tool when the latter is in working contact with the work, means responsive to twisting of the torsion bar for transmitting the torque from the motor to the tool under load independently of the bar, and mechanism also responsive to twisting of the said bar for altering the speed of the feed of the tool towards the work by said feeding mechanism.

2. A machine tool according to claim 1, characterized thereby that the said torque transmitting means is disposed concentrically with respect to and embraces the torsion bar.

3. A machine tool according to claim 2 wherein the said torque transmitting means comprises relatively movable members connected respectively to the tool and the motor and having contact surfaces held out of contact with each other by said torsion bar when the tool does not contact the work and brought into contact by twisting of the bar under load.

4. A machine tool according to claim 1 wherein the said mechanism for altering the speed of the feed comprises a rod disposed within a longitudinal bore in the 7 motor shaft, together with means at one end of the rod responsive to twisting of the torsion bar for longitudinally displacing the rod in the bore, and speed control devices operatively connected with the other end of said rod.

5. A machine tool according to claim 4 wherein the said speed control devices comprise a hydraulic system, a valve operatively connected in said system, an electric circuit containing an electric magnet, said magnet having an armature connected to the valve, and an electric switch controlling said circuit and arranged for actuation by displacement of said rod.

References Cited in the file of this patent UNITED STATES PATENTS 2,410,695 Werner Nov. 5, 1946 2,411,162 King Nov. 19, 1946 2,422,905 Jackson June 24, 1947 FOREIGN PATENTS 391,479 Great Britain Apr. 20, 1933 

